REPRODUCTION AND DISPERSAL 



893 



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if an inflorescence is cut off and allowed to strike root in a moist chamber 

 the tip grows into a vegetative shoot (figs. 1199, 1200). The oldest 

 buds develop into the usual 

 flowers, while younger buds de- 

 velop into cleistogamous flowers 

 without prominent corollas; still 

 younger buds develop only the 

 calyx, and the very youngest 

 lateral buds, as well as the ter- 

 minal bud, develop vegetative 

 shoots. If a flowering shoot of 

 Myriophyllum heierophyllum is 

 transferred from a pond to a 

 covered aquarium, it becomes 

 transformed into a vegetative 

 shoot. Ajuga repians has three 

 phases, a rosette, a flowering 

 shoot, and a stolon, and any of 

 the three can be induced at any 

 time by supplying the requisite ex- 

 ternal conditions. If the flowers 

 of Opuntia are removed from the 

 plant and placed in the soil, they 

 soon strike root and give rise to 

 vegetative shoots. Most striking 

 of all, perhaps, are the reactions 

 of the xerophyte, Sempervivum, 

 which also has three phases, comparable to those of Ajuga; vegetative 

 activity may be made to continue indefinitely, stolon formation may be 

 eliminated, and phenomena unusual in nature (such as rosette for- 

 mation at the stem apex, and the transformation of the inflorescence 

 into a vegetative shoot) may be induced at will. 



Reversibility of stages is not confined to the seed plants; if a fruiting shoot of 

 Selaginella lepidophylla is cut off and placed in the soil of a moist hothouse, it be- 

 comes transformed into a vegetative shoot, even developing rhizophores. Reversi- 

 bility can be induced also in animals, for if a polyp of the hydroid. Campanularia, 

 is brought into contact with a sohd body, it gradually becomes undifferentiated and 

 finally develops into a stolon, whereas removal to the original habitat soon results in 

 a transformation back to a polyp. It may be noted finally that reversibility is the 

 usual thing in the pineapple, a vegetative shoot developing at the apex of the fruit. 



Figs. 1199, 1200. — Variation in the flower- 

 ing shoots of Veromca Chamaedrys : 1199, an 

 ordinary flowering shoot with buds, flowers, 

 and young fruits; 1200, a similar shoot that 

 was placed in moist air at the inception of 

 anthesis; note the metamorphosis of the upper ■ 

 part into a leafy shoot. — From Klebs. 



